Cameras have been used by people for many hundreds of years. Some early cameras were used to project an inverted image onto a screen so that the image could be manually traced. Photographic camera technology was not developed until the 1800s. These cameras used chemically coated paper or film. Film technology is still used today. However, digital cameras (cameras that do not use film, but instead use an image sensor that captures light and converts the light into an electronic signal based on a wavelength or intensity of the light) have become more popular than film type cameras. Cameras today are quite ubiquitous in that nearly every modern phone includes a camera and security systems rely on camera technology. Camera technology is now used in a wide array of applications including traffic control systems and advertising, where the cameras can help achieve better traffic conditions or help determine if the advertiser's message is reaching the public.